Hi Kenny,
Thanks for looking into this. We do not set any client-side connection timeout. Here is the java code we use to make the api call. Please note that we are using batchSize=1.
URL url = new URL("https://<marketo url>/rest/v1/list/<list id>/leads.json?access_token=<access token>&batchSize=1&fields=<comma separated fields>");
urlConn = (HttpsURLConnection) url.openConnection();
urlConn.setRequestMethod("GET");
urlConn.setAllowUserInteraction(false);
urlConn.setDoOutput(true);
urlConn.setRequestProperty("Content-type", "application/json");
urlConn.setRequestProperty("accept", "application/json");
int responseCode = urlConn.getResponseCode();